I don't think that using dpkg's dependency mechanisms is appropriate
here, because people are always compiling their own kernels.
Perhaps the kernel image prerm should check that the kernel being
removed isn't the default one in lilo.conf, and/or that it isn't the
only one.
I think that something similar might apply to the modules package -
surely having modules installed shouldn't be required for someone who
compiles their own kernels without modules ?
Ian.